Modulation of particle residence time in powder size-dependent ZrC coating on carbon-carbon composite with vacuum plasma spray

Recently, carbon-carbon (C/C) composites have been widely employed in various application fields due to their exceptional properties, but their oxidation at relatively low temperature around 500 °C poses a challenge to be used in high-temperature conditions. To address the drawback, the coating of ultra-high temperature ceramic (UHTC) layer on the C/C composites has been suggested as one of promising solutions. However, the quality of UHTC coating layers obtained through vacuum plasma spraying (VPS) is heavily influenced by the size of the introducing raw powders to coat the layers. Therefore, we investigated the size effects of ZrC powders in the range of (10–50) μm, one of UHTCs, to optimize the coating quality. By modulating process conditions, the coating quality with thick ZrC layer having lower porosity was obtained when using the powder around 34 μm. From the results, we found the gas residence time related to the particle velocity in the plasma flame is one of key parameters to be modulated by VPS operational parameters, which could improve the quality of the coating layer even for large powder cases.